Create 0652-find-duplicate-subtrees.js

Author: aadil42

javascript/0652-find-duplicate-subtrees.js

@@ -0,0 +1,52 @@
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val, left, right) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.left = (left===undefined ? null : left)
+ *     this.right = (right===undefined ? null : right)
+ * }
+ */
+/**
+ * Hashing 
+ * Time O(n^2) | Space O(n^2)
+ * https://leetcode.com/problems/find-duplicate-subtrees/
+ * @param {TreeNode} root
+ * @return {TreeNode[]}
+ */
+var findDuplicateSubtrees = function(root) {
+    
+    const stringHash = {};
+
+    const makePreOrderStr = (node, str) => {
+        if(!node) return str + "-" + "null";
+        
+        const str1 = makePreOrderStr(node.left, str + "-" +node.val);
+        const str2 = makePreOrderStr(node.right, str1);
+
+        return str2;
+    }
+
+    const duplicates = [];
+
+    const dfs = (node) => {
+        if(!node) return;
+        const str = makePreOrderStr(node, "");
+
+        if(!stringHash[str]) {
+            stringHash[str] = [];
+        }
+        
+        stringHash[str].push(node);
+
+        dfs(node.left);
+        dfs(node.right);
+    }   
+
+    dfs(root);
+    
+    for (let key in stringHash) {
+        if(stringHash[key].length > 1) duplicates.push(stringHash[key][0]);
+    }
+
+    return duplicates;
+};